1. Field of the Invention
The present invention relates in general to an automotive power plant structure which, for producing a drive power and transmitting the power to driven wheels, consists of an engine part and a transmission part, and more particularly, the present invention relates to a low-noise level automotive power plant structure which has a high rigidity in construction to reduce engine noise emitted therefrom.
2. Description of the Prior Art
Japanese Utility Model First Provisional Publication No. 58-53826 shows an internal combustion engine which is constructed rigid for reducing noise emitted therefrom.
As is seen from FIGS. 9, 10, and 11 of the accompanying drawings, the engine disclosed by the publication has a unique construction practically applied thereto. That is, the engine comprises a cylinder block 10 having a lower skirt section 12 which is bulged outwardly and extends downwardly to define thereinside an upper part of a crankcase (no numeral). A plurality of main bearing bulkheads 14 are parallelly aligned and disposed inside of the skirt section 12. Each bulkhead 14 is formed with a bearing section (no numeral).
A ladder beam structure 16 is securely connected to the bottom portion of the cylinder block 10 and includes, as is seen from FIGS. 10 and 11, a plurality of main bearing cap sections 18 each having both ends integrally connected to respective side beam sections 20 and 22. Each bearing cap section 18 is secured at its top portion onto each bearing bulkhead 14 by means of cap bolts 24 so as to associate with the bearing section of the bulkhead 14, thereby forming a cylindrical bore 26 in which the journal of a crankshaft (not shown) is rotatably supported. An oil pan 28 is secured to the bottom portion of the ladder beam structure 16.
With the construction as described hereinabove, the rigidity of the bearing cap sections 18 is increased and the vibration of the skirt section 12 is reduced. Thus, the engine noise can be reduced to a certain low level.